oh forget get some skybox brushes on there right now.
Shut up you don't know think about mapping, i'm not play testing the map YET i don't need loving Skybox brushes, this is how a map in loving development works!
If i place a bunch of brushes no one in the topic will even know what, they are looking at in the screen shots! did you even read this topic at all?
Put a lot of clouds in the sky.
Like meteors hit the earth and dust clouds covered the land so nothing could grow.
add a few meteors too
It doesn't work like that.
add tumbleweeds. 
I really don't think i can.